What is the maximum number of characters for a USSD message?

The maximum size of a USSD message is 160 bytes. For GSM 7 Bit encoded messages this results in a limit of 182 characters. If you choose UCS2 encoding your USSD message can have a maximum of 80 characters.

The effective and maximum payload that EMnify guarantees to deliver for a USSD message is 144 bytes (164 characters for a GSM 7 bit encoding and 72 characters for UCS2 encoding).